SHBG is short for Sex Hormone Binding Globulin.
This test is rarely ordered, which is unfortunate because it can give you a lot of information about the hormones in your body.
High levels can lead to symptoms of excess estrogen, excess thyroid, and low testosterone.
Low levels can lead to symptoms of low thyroid, low estrogen, and excess testosterone.
In this article, I will discuss how to interpret your SHBG test results, and list some common causes of elevated levels and low levels.
I will show how SHBG can be used to monitor your thyroid function if you are on thyroid medication.
I will also discuss some things that you can do to help you get your SHBG level back into the optimal range whether it is high or low...
SHBG is an acronym for sex hormone binding globulin.
It does what it sounds like it does - it binds up sex hormones.
Why is that important?
In order to understand this better we need to discuss how hormones work in general.
The vast majority of hormones in your body are bound to proteins in the bloodstream. This helps to stabilize the hormone so it can get to the targeted cells all over the body.
While it is bound, however, it is inactive and not available for the cells to use.
In order for the hormone to be active, it must break away from the protein. This makes it a "free" hormone and it can then enter the cells and turn on the cellular function it is designed to do.
This is called the Free Hormone Hypothesis.
The "free" hormones are therefore the "active" hormones.
The amount of "free" hormones is much smaller than the amount of "bound" hormones.
This protein binding is one of the ways that the body uses to regulate the hormone levels.
So what about SHBG?
SHBG levels naturally increase as we age. Since most hormone levels naturally decline as well, this makes a deficiency of those hormones (especially testosterone) even more pronounced.
Sex Hormone Binding Globulin binds to several different hormones. The body uses SHBG to inactivate these hormones in the bloodstream.
Too much of it can be bad because it can bind so much of the hormone that we can have symptoms caused by a lack of that hormone.
Too little can also be bad because it can cause an excess of certain hormones which also causes symptoms.
Even small changes in SHBG can cause substantial symptoms and problems.
SHBG has a stronger affinity for some hormones that others.
It will preferentially bind to sex hormones in this order (from highest affinity to lowest):
As you can see, SHBG has a greater affinity for androgens than estrogens.
You can therefore predict the symptoms you may have by knowing the effect that the SHBG level has on your androgen levels.
For example, if you have an elevated SHBG, it will bind DHT and testosterone which will cause symptoms of low testosterone (weight gain, depression, increased belly fat, loss of muscle, etc.).
With low levels of SHBG, you will have more unbound or free testosterone which will cause symptoms of high testosterone (acne, facial hair growth, PCOS, etc).
Hopefully you can see why it's important to check your SHBG level if you are having any symptoms of hormonal imbalance to help you and your doctor determine what issues are going on in your body.
The optimal range for SHBG is 60-80 nmol/L. Any level below or above this range should be investigated.
There are several things that I will list below that can elevate SHBG levels.
An increase in either or both of these hormones will stimulate the liver to increase SHBG production.
A SHBG level > 80 nmol/L is considered too high.
Another hormone to keep in mind that is closely linked to SHBG is cortisol.
Cortisol is our stress hormone. In times of increased stress (physical or mental), our adrenal glands increase cortisol production.
An elevated cortisol level stimulates the liver to increase SHBG production.
Please realize that an elevated level of SHBG does not in itself cause any symptoms.
The symptoms are caused by the effect that the high SHBG level has on hormones in the body.
Most of the symptoms will be due to either excess estrogen and/or low testosterone:
If the elevated SHBG is caused by the situation of a high thyroid level (hyperthyroidism or excessive oral thyroid medication), you can also have symptoms related to the elevated thyroid such as tremor, palpitations and weight loss.
Treating an elevated SHBG has more to do with finding the cause of the elevation rather than treating the elevated SHBG itself.
There are several things you should consider doing:
The ratio of these 2 hormones is more important than the numbers themselves.
Check the levels in the middle of your cycle (2 weeks after your last period) for the best results.
If the ratio of estrogen:progesterone is >10:1, you have estrogen dominance that needs to be addressed.
If your estrogen level is normal, then it is highly likely that your thyroid is the culprit of your elevated SHBG.
Check a complete thyroid panel, especially free T3 and free T4.
If these are elevated and you are on thyroid medication, you may need to lower your dose or even change your thyroid medication.
If you aren't on thyroid medication, you need to have more testing done ASAP to find the cause of your elevated thyroid (most likely Grave's Disease).
I discuss several techniques to better manage your stress in my article on Adrenal Fatigue.
Low SHBG is more difficult to detect and often harder to treat.
As a result, it is often ignored much more than an elevated SHBG.
A low SHBG typically occurs in menopausal women or patients with hypothyroidism (low thyroid).
So if your SHBG is < 60 nmol/L, you should look at estrogen and thyroid as the probable causes if you are menopausal.
If you are still menstruating, then hypothyroidism is the likely cause.
If one or both of those hormones is low, SHBG levels will drop which will increase free testosterone, paving the way for conditions such as PCOS.
This series of hormone imbalances also appears to set up a person to develop insulin resistance.
In fact, a low SHBG level has been shown to be a strong predictor for type 2 diabetes in both men and women.
The symptoms associated with a low SHBG are typically caused by low thyroid hormone, low estrogen, and elevated testosterone. The include:
Keep in mind that your individual symptoms will depend on which hormones are out of balance and to what extent.
If you have a low SHBG, you should consider the following things:
Compare these tests with their optimal levels to determine if you have a thyroid issue.
If your thyroid function is low, it is probably affecting your SHBG level and you will need to consider taking a thyroid medication and doing other things to help boost your thyroid function.
After menopause, your estrogen levels will drop which can drop your SHBG level.
If that is the case in your situation, you might need to consider bioidentical hormone replacement therapy.
If your SHBG level is low, there will be less of it to bind to testosterone, so it may cause your free testosterone level to rise.
This can usually be alleviated by maximizing your thyroid medication which will raise your SHBG level.
One final benefit of checking your SHBG level is it a good indicator of the thyroid function in your body.
In states of low thyroid function, the SHBG level drops.
In states of high thyroid function, the SHBG level rises.
This allows the SHBG to be used as a marker to assess the thyroid hormone absorption and cellular function.
If you have low SHBG and hypothyroidism, you should test your SHBG level at the beginning of treatment to assess if you are on the right type of thyroid hormone and the right amount.
If you are taking a T4 only thyroid medication and your SHBG level does not increase, you may have a problem with peripheral conversion of T4 into active T3.
You therefore may need to change to a natural dessicated thyroid (NDT) or add T3 to your current regimen.
On the flip side, if after starting your thyroid medication your SHBG level rises > 80 nmol/L, that is an indication that your dose is too high and it should be reduced.
The sex hormone binding globulin level gives us important information on the status of several hormones in the body.
A high level is typically caused by estrogen excess and excess cortisol.
A low level is typically caused by low thyroid. It also is an indicator that you may be having issues with insulin resistance.
The key to treating an abnormal SHBG level is to identify what is causing the abnormality and correct it.
Doing this will help return the SHBG level to the optimal range and reduce symptoms.
Now it's your turn...
Do you have an abnormal SHBG level?
Have you identified the cause or causes?
Please leave your comments below.
Dr. Whelchel is a family physician who specializes in functional medicine, especially hormone optimization. He has over 20 years experience in private practice managing patients with various medical issues. His passion is helping patients reach their full potential of wellness and quality of life. He grew up in the Texas Panhandle where he currently lives. He is married and has 3 awesome children.